1. Field of the Invention
This invention relates to an ink jet recording apparatus and a capping device, and more particularly to an ink jet recording apparatus in which a capping device is urged against the nozzle portion of an ink jet printer to accomplish the ink non-discharge recovery operation and to a capping device in such apparatus.
2. Related Background Art
In an ink jet printer flying liquid droplets are discharged from an orifice at the end of a nozzle toward recording paper by various means to thereby accomplish dot recording.
In the ink jet printer of this type, the use of liquid ink causes occurrence of a non-discharge phenomenon such as the non-discharge of ink resulting from the clogging by desiccation of the ink, the clogging by adherence of dust, or the production of bubbles attributable to remaining gas.
So, as at the beginning of recording, ink is forcibly discharged to release the non-discharge state.
During such non-discharge recovery operation, ink is not discharged toward recording paper, but ink is discharged with the nozzle portion being covered with a cap.
There are various structures of this cap, and the structure adopted most often is one in which an ink absorbing member comprising, for example, a sponge material, is provided in the cap and ink is discharged toward and absorbed by the absorbing member.
In the cap of such a structure, if the ink absorbed by the absorbing member is not discharged by some means, the absorbing member will contain therein more ink than it can absorb and will thus become useless for the non-discharge recovery operation.
As a method of removing ink from the ink absorbing member in such a state, a system for squeezing out ink by the provision of a throttle mechanism has been widely adopted.
As such a throttle mechanism, there would come to mind a mechanism of a structure in which an ink absorbing member is contained in a frame member of substantially L-shaped cross-section and a throttle plate is disposed below the absorbing member to squeeze out ink.
However, in the mechanism of the above-described structure, all of the absorbing member, the frame member supporting it and the throttle plate are disposed horizontally, and this has sometimes led to a problem that when the absorbing member is throttled by the throttle plate, ink is forced out forwardly of the absorbing member as well and by so throttling, the head side is stained by ink.
The phenomenon that ink is forced out forwardly of the ink absorbing member occurs in the forward lower corner of the absorbing member and therefore, ink is liable to stain especially the head side.
As another example of such a throttle mechanism, a structure is also conceivable in which, for example, two upper and lower throttle plates are provided and an ink absorbing member is sandwiched between the two throttle plates so that the absorbing member is pressed from above and below to thereby squeeze out the absorbed ink.
However, the adoption of such a throttle mechanism has sometimes led to the following problem.
That is, the ink jet printer has been made compact and the nozzle itself has also been made compact and therefore, the cap has also unavoidably been made compact correspondingly thereto, and to make the throttle mechanism function effectively in the compact cap, it must be contained in a narrow space and in such a case, squeezed ink will make a bridge between it and the wall surface of the case of the cap or will remain in the cap.
If ink remains in the cap, the ink adheres to and stains recording paper or the like or the ink adheres to the nozzle side, and in some cases this has led to an inconvenience that proper discharge of ink cannot be accomplished.
Also, in a structure wherein two upper and lower throttle plates are brouhgt close to each other to squeeze out ink, the squeezing operation is effected substantially in the central portion of the narrow space in the cap, and the throttle plates are near the upper and lower side walls of the cap and therefore, a bridge is created inevitably.
Further, sponge-like formed synthetic resin is widely used for the ink absorbing member employed in such a throttle mechanism.
However, such an ink absorbing member has the property of swelling by absorbing ink.
On the other hand, the dimensional accuracy between the ink absorbing member and the head is required to be considerably high in order to positively absorb ink.
Accordingly, unless the absorbing member is mounted with its rate of swelling being accurately taken into account, the dimension thereof will become wrong.
Heretofore, however, the absorbing member has been held by being adhesively secured to the support frame side or by a complicated structure, and this has sometimes led to a problem that when the absrobing member swells, the dimensional accuracy thereof is not obtained and accurate and positive ink absorption cannot take place.
Also, there are cases where the absorbing member must be replaced with a new one after it has been used for a predetermined period of time, and in preparation for such cases, the absorbing member must be of a readily replaceable structure and must be held on the support frame side, but the absorbing member of the conventional structure has been very cumbersome to mount and dismount.
The considerably complicated flow path of an ink jet printer or the like for supplying ink is often constituted by a tube.
Through such a flow path, supply of ink is effected by the driving of a pump or a valve.
However, in the flow path system, there is a flow path in which flow of ink takes place, without pressurization, in addition to the flow path in which flow of ink is effected by the pressure of a pump or the like.
An example of it such as a drain tube which directs into a drain tank the waste ink such as the ink squeezed out from said absorbing member.
Such a drain tube can be a thin tube simply connecting the ink collecting unit to the drain tank and adapted so that ink flows therethrough from gravity.
Such a drain tube is widely used not only in ink jet printers but also in various apparatuses handling fluid.
The use of a thin tube as such a drain tube is for the purpose of facilitating piping and preventing desiccation of ink or other liquid in the flow path system.
The flow path structure in which flow of liquid is effected by the use of the thin tube as described above and in accordance with the law of gravity suffers from the following problem.
Where, the diameter of the tube constituting the flows path is small, the influence of surface tension is great, and where liquid such as ink is not flowing continuously in a great deal, for example, where liquid flow intermittently in the form of liquid droplets (individually independent small volumes of liquid, i.e., small amounts of liquid), meniscus by surface tension is produced on the upper and lower end surfaces of the small amounts of liquid in the tube and these small amounts of liquid stop in the intermediate portion of the tube.
When such a phenomenon occurs at a plurality of locations in the tube, the tube becomes closed up by these small amounts of liquid to block the passage of the succeeding liquid, and this has sometimes led to occurrence of overflow or the like.
One means for eliminating such an inconvenience is to increase the diameter of the tube, whereas an increased diameter of the tube not only makes piping difficult, but also increases the amount of flow of air, which has sometimes led to desiccation of the liquid.